1. Field of Invention
The present invention relates to a torque-providing tool and, more particularly, to a torque-setting device for use in a torque-providing tool.
2. Related Prior Art
There are torque-providing tools such as wrenches and screwdrivers. Such a torque-providing tool includes a handle and a driving unit connected to the handle. The driving unit can be engaged with a bit, and the bit can be engaged with a fastener such as axle and a nut. Thus, the torque-providing tool is operable to provide torque to the fastener. To provide certain values of torque to certain fasteners, there have been devised torque-indicating devices. Such a torque indicating device includes a strain gauge connected to the handle or the driving unit, a display and a circuit for connecting the strain gauge to the display. Thus, a value of torque is converted to strain in the strain gauge. The circuit calculates the strain and sends a corresponding signal to the display, and the display shows the value of torque.
To warn a user of a fact that a value of torque has been reached, there have been devised torque-setting devices so that a click is given when a corresponding value of torque is reached. Such a torque-setting device includes a strain spring connected to the strain gauge, an axle inserted in the strain spring and a nut engaged with the axle and abutted against the strain spring. Rotation of the axle relative to the handle is not allowed.
When the nut is rotated relative to the axle, the extent to which the strain spring is compressed is changed, and a value of torque is set. However, the setting of the value of torque is not precise. Moreover, the nut might be rotated accidentally, thus setting an undesired value of torque.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.